The present invention pertains to an ink set comprising at least two inks wherein one ink comprises a reactive carbonyl-group(s) containing species and a second ink comprises a reactive amine groups containing species. When the two inks are printed on a substrate in an overlapping arrangement, the reactive amine and reactive carbonyl species can crosslink to form a more durable image.
Inkjet printing is a non-impact printing process in which droplets of ink are deposited on print media, such as paper, to form the desired image. The droplets are ejected from a printhead in response to electrical signals generated by a microprocessor. Inks used in such recording are subject to rigorous demands including, for example, good dispersion stability, ejection stability, and good fixation to media.
Inkjet printers offer low cost, high quality printing and have become a popular alternative to other types of printers such as laser printers. However, inkjet printers are presently unable to match the speed of laser printers and the durability of the laser printed images. Inkjet prints with increased durability would be highly advantageous.
With regard to increasing durability of inkjet prints, U.S. Pat. No. 4,694,302 describes a two pen configuration wherein one pen contains aluminum chloride in aqueous vehicle and the second pen contains a colored ink with carboxymethyl cellulose (CMC) in aqueous vehicle. When jetted together on a substrate, an insoluble salt of CMC is formed, producing a protective coating. The print was reported to be very water-fast.
U.S. Pat. No. 6,020,397 describes an inkjet printing process wherein a first liquid comprising aziridine and a second liquid comprising a polymer reactive with aziridine are sequentially applied to a substrate, thereby forming an aziridine-crosslinked polymer. Good ink adhesion was reported.
U.S. Pat. No. 6,503,307 describes a set of liquid compositions wherein a first liquid comprises a first water-soluble compound having an ethylenically unsaturated double bond with an alpha-electron withdrawing group and a second liquid comprises a second water soluble compound having an active hydrogen addable to the first compound. Colorant can be present in either liquid. When printed together on a substrate, the first and second liquids can react to form a polymeric film. Water and abrasion resistance are reported to be excellent.
U.S. Published Application No. 2002/0156153 describes a two part fixative comprising (1) a reactive monomer or oligomer, selected from the group of isocyanates and epoxy terminated oligomers, in a vehicle and (2) at least one second component, selected from polyols and polyvinyl alcohols, and base catalyst. The reactive monomer or oligomer reacts with the second component on the print medium to form a polymer. Water-, smear- and smudge-fastness are reported to be enhanced.
Still there is a need for, and it is an objective of this invention to provide, inks and printing methods that provide more physically durable inkjet images.